Control for an air heater



y 28, 1964 P. G. BARTLETT ETAL 3,142,479

CONTROL FOR AN AIR HEATER Filed Oct. 9, 1961 AHUMIDJTAT 53 INVENTOR-S PETER G. BARTLETT BYBH R\CHARD C. BARTLETT MW QM-1211M AHornys United States Patent 3,142,479 CONTROL FOR AN AIR HEATER Peter G. Bartlett and Richard C. Bartlett, both of Indianapolis, Ind, assignors to Bartlett Laboratories, Inc., Indianapolis, Ind., a corporation of Indiana Fitted Oct. 9, 1961, Ser. No. 143,672 Claims. (Cl. 263-19) The present invention relates to a control and sensing device finding an important utility in heating and drying devices such as are used on the farm for drying grain or any commodity requiring a blast of heated air to affect the drying operation.

As is well known, grain and the like is frequently stored in silos, corn cribs or similar structures. In order to dry such material and to prevent spoilage thereof, it is necessary to provide a large amount of low humidity air which is conventionally passed through an air conduit into the lower portion of the structure, through the grain and out the top of the structure. When necessary, heat is added to the air in order to lower the humidity thereof.

Various devices have been used to add the heat to the moving air, practicallly all of which include a shield positioned in the air conduit for shielding the flame and preventing its being extinguished by the blast of air. The products of the combustion from the flame pass directly into the air to heat it and lower its humidity before the air moves through the grain.

Obviously, it is necessary to provide safe means for maintaining the fuel ignited and for preventing unburned fuel from passing into the air conduit. It is also necessary to prevent fuel from passing into the air conduit except when air is being moved through the conduit. Consequently, a primary object of the present invention is to provide an improved control arrangement capable of causing gas or other fuel to flow only when a large volume of air is flowing past a burner and only when the burner igniter is hot.

A further object of the present invention is to provide an improved sensing arrangement.

Still another object of the present invention is to provide an improved control arrangement for a grain dryer.

Still a further object of the invention is to provide an improved control arrangement for a heating and/ or drying device.

One embodiment of the present invention comprises a control arrangement including a power source and an electric igniter. The igniter is positioned to ignite a burner positioned behind a shield Within an air conduit. A thermocouple is positioned with its hot junction behind the shield and adjacent the igniter and its cold junction removed from the igniter and within the air stream in the conduit. There is also provided means for electrically connecting the power source and the igniter, said means being operated by the thermocouple when its junctions are the same temperature and means for providing fuel to the burner, said means being operated by the thermocouple when its junctions are different temperatures.

The full nature of the invention will be understood from the accompanying drawings and the following description and claims.

FIG. 1 is a longitudinal section of a grain dryer adapted to be connected to the lower portion of a grain bin for drying grain therein.

FIG. 2 is a view similar to FIG. 1 but enlarged and with portions broken away to show internal details.

FIG. 3 is an electrical schematic diagram of the control arrangement of the present invention.

Referring more particularly to the drawings, there is illustrated a conduit 10 which is conventionally connected at its end 11 to the lower portion of a grain bin whereby air may be pumped through the conduit 10 by a fan 12 3,142,479 Patented July 28, 1964 and into the grain bin through the grain for drying the grain. At the intake end of the conduit 10, there is provided a screen 15 to prevent large objects from being sucked into the conduit. The fan 12 includes a suitable rotatable blade arrangement 16 and a motor 17 suitably mounted in fixed relation to the conduit 10.

Positioned downstream of the fan 12 is a burner assembly 20 which includes a cup-shaped shield 21 fixedly mounted centrally of the conduit 10 and upon a cupshaped member 22 having a plurality of orifices 25 therein. The burner assembly further includes piping 26 which mounts the member 22 and conducts a gas-air mixture thereinto for passage through the orifices 25. The member 22 is mounted on the piping 26 in sealed relation so that no gas passes between the member and piping.

Adjacent the inside wall of the conduit 10, there is located a conventional air-gas Venturi arrangement 27 which operates to mix air moving through the conduit 10 with pure gas being pumped through piping 30, the products of such mixing passing into the piping 26. The function of the burner assembly 20 is to move gas into the conduit, burn the gas and distribute uniformly the heated products of combustion throughout the air moving through the conduit. The radial and downstream extending vanes 31 fixed to the shield 21 assist in the uniform distribution of the products of combustion into the conduit 10. Of course, the vanes could be eliminated, if desired, or other uniform distributing or mixing means might be used.

Steel tubing 32 is mounted at its threaded end 35 so as to extend through the conduit 10 and radially inwardly thereof with its other end 36 received through the wall of the cup-shaped shield 21. The tubing 32 is fixed in this position by means of a pair of nuts 37. Mounted uponthe most inward end 36 of the tube 32 is an electrical igniter 4% which in the illustrated embodiment comprises a coil and which alternatively may comprise a cylinder of high resistance metal. It will be noted that the igniter 40 is located within the shield 21 and adjacent the orifices 25 out of which is expelled the gas-air mixture for burning.

Mounted within the tubing 32 by means of ceramic in sulators 41 is a thermocouple 42 including a pair of junctions 45 and 46 which, during the operation of the device, become the hot and cold junctions, respectively. The metal making up the thermocouple may include Alumel at 47 and Chromel at 50 although any suitable thermocouple metals may be used. The voltage created by the thermocouple is tapped off by means of copper wires 51 and 52 which extend through the ceramic insulators 41 to provide a mounting for the thermocouple.

Referring to FIG. 3, the operation of the present device will be described in connection with a description of the electrical circuitry of the arrangement. A power. source 53 is in series with a humidstat switch 54. The switch 54 is suitably controlled to close whenever the. humidity within the grain bin or any other suitable checkpoint rises above a predetermined value. It should be noted that the fan 12 is intended to operate continuously during the complete drying cycle which, for example, may be of two or three days duration. Obviously, during this time, the humidity may vary greatly between values. at which it is unnecessary to add heat to the air and values at which it is necessary to so add heat for proper drying.

Assume then that the fan 12 is operating and blowing air past the shield 21 and vanes 31 and that the humidity is suificiently high to close the, switch 54. Power will be providedfrom the power source 53 through the switch 54, the contact arm 55 and the contact 56 to the ignition coil 40. The ignition coil will heat up and will heat its surroundings including the thermocouple 42. The air, however, moving rapidly over the tube 32 will cool the cold junction 46 with relation to the hot junction 45 which is located inside of the ignition coil 40. This cooling action will cause a voltage drop to be placed across a solenoid 57 forming a part of a relay 60. Energization of the solenoid 57 will cause the relays contact arm 55 to disengage the contact 56 and to engage the contact 61 causing the voltage of the power source to be placed across the solenoid 62. The relay 60 is conventional and may be, for example, a Potter and Brumfield Relay Model 555D, manufactured by Potter and Brumfield, Inc., of Princeton, Indiana.

The solenoid 62 controls a valve indicated schematically at 63 including valve head 63A, controlling the flow of fuel into the pipe 30. The valve 63 is conventional and may be, for example, an ASCO model 826213, manufactured by Asco Automatic Switch Company, of Florham Park, New Jersey. Whenever the solenoid 62 is energized, the valve is operated to permit gas to flow into the pipe 30 for mixture by the Venturi and further flow into the piping 26 and through the orifices 25. Because the ignition coil is hot, the gas-air mixture which thus starts to flow through the orifices is ignited. As the burning continues, the coil 49 and the hot junction 45 of the thermocouple are maintained hot. The cold junction 46 of the thermocouple is continuously cooled by the operation of the fan 12 in blowing air toward and past the shield 21 and vanes 31.

If the gas flame should go out, or if the fan should cease operation, the temperature diflerential between the hot and cold junctions 45 and 46 would no longer be maintained. Suitable conventional resilient means 63B are provided within the gas valve for closing the valve whenever the solenoid 62 is deenergized. Also, the relay 60 includes conventional resilient means for returning the contact arm 55 to engagement with the contact 56 and out of engagement with the contact 61 when the solenoid 57 is deenergized. It will, therefore, be evident that the lack of temperature differential between the hot and cold junctions 45 and 46 will cause the deenergization of the solenoid 57 and the deenergization of the solenoid 62 whereby the gas valve is closed.

Of course, if the fan has ceased operation, no further gas will be permitted to flow through the orifices. However, if the flame has merely been blown out, the return of the contact arm 55 to engagement with contact 56 will again produce a voltage drop across the ignition coil 40 so as to heat it. Since the fan is still operating, the heated igniter will produce a voltage differential between the junctions 45 and 46 will cause the solenoid 57 to reopen the gas valve reigniting the device. Of course, whenever the humidistat switch 54 is open and the humidity is below the predetermined value, no power is provided to the igniter 40 or to the gas valve solenoid 62 whereby the gas is maintained in a shut-ofi condition and the ignition coil is not heated.

From the above description, it will be obvious that the present invention provides an improved sensing arrangement and also an improved control arrangement. The structure making up the present invention is relatively inexpensive and is capable of operating the grain dryer in the desired manner. Thus, the present structure is capable of causing gas to flow only when air is flowing through the conduit and when the ignition coil is heated.

While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention and the scope of the claims are also desired to be protected.

The invention claimed is:

l. A control arrangement comprising a shield, means operable to move a stream of air toward and past said shield, said shield reducing the air flow in a first location downstream of and adjacent said shield but not reducing the air flow in a second location elsewhere of said first location an electrical power source, an electric igniter at said first location, a thermocouple having one junction at said first location and the other junction at said second location, means for feeding a combustible mixture to said shield, means for electrically connecting said power source and igniter, said last means being operable by a potential of given strength to disconnect said power source and igniter, and a circuit connecting said thermocouple to said last means whereby production of an electric potential of given strength by said thermocouple disconnects said power source and igniter,

2. A control arrangement comprising an electrical power supply, an electric heater in a first circuit with said power supply for igniting fuel, a thermocouple having a hot junction adjacent said heater and a cold junction removed from said heater, a fuel valve controlling fuel to said heater, a solenoid in a second circuit with said power supply and controlling said fuel valve and arranged to open said valve when said solenoid is energized, said valve including means normally maintaining said valve in closed position except when said solenoid is energized, a relay including a further solenoid and including contacts in said second circuit which are closed to complete said second circuit when said further solenoid is energized, said further solenoid being in a third circuit with said thermocouple, said relay including contacts in said first circuit which are closed to complete said first circuit when said further solenoid is deenergized.

3. A control arrangement comprising a conduit, means for moving air along said conduit, a burner including a shield positioned in said conduit, said shield reducing the air flow in a first location downstream of and adjacent said shield but not reducing the air flow in a second location within said conduit elsewhere of said first location, said burner having an orifice arranged to exhaust fuel at said first location, an electric heater at said first location for igniting said fuel, a thermocouple having a hot junction at said first location and a cold junction at said second location, and an electrical power source in a first circuit with said electric igniter, a relay including a solenoid and including contacts in said first circuit which are closed to complete said first circuit when said solenoid is energized below a given strength, said solenoid being in a second circuit with said thermocouple whereby said solenoid can be energized above and below said given strength by said thermocouple.

4. A control arrangement comprising means for moving air, a burner including a shield positioned in the air stream from said means, said shield reducing the air flow in a first location downstream of and adjacent said shield but not reducing the air flow in a second location elsewhere of said first location, said burner having an orifice arranged to exhaust fuel at said first location, an electric heater at said first location for igniting said fuel, a thermocouple having a one junction at said first location and its other junction at said second location, an electrically operated fuel valve controlling fuel to said orifice, and an electrical power source in a first circuit with said electric igniter and in a second circuit with said electrically operated fuel valve, a relay including a solenoid and a first set of contacts in said first circuit which are closed to complete said first circuit when said solenoid is energized below a given strength, said relay including a second set of contacts in said second circuit which are closed to complete said second circuit when said solenoid is energized above said given strength, said thermocouple being in a third circuit with said solenoid and energizing said solenoid below said given strength whenever the temperature diflerential across the thermocouple is below a given amount and energizing said solenoid above said given strength when the temperature differential is above a given amount.

5. A control arrangement comprising means for moving air, a burner including a shield positioned in the air stream from said means, said shield reducing the air flow in a first location downstream of and adjacent said shield but not reducing the air flow in a second location within said conduit elsewhere of said first location, said burner having an orifice arranged to exhaust fuel at said first location, an electric heater at said first location for igniting said fuel, a thermocouple having a hot junction at said first location and a cold junction at said second location, a fuel valve controlling fuel to said orifice, a solenoid controlling said fuel valve and arranged to open said valve when said solenoid is energized, said valve including means normally maintaining said valve in closed position except when said solenoid is energized, a power supply in a first circuit with said electric heater and in a second circuit with said solenoid, a relay including a further solenoid and a first set of contacts in said first circuit which are closed to complete said first circuit when said further solenoid is energized below a given strength, said relay including a second set of contacts in said second circuit which are closed to complete said second circuit when said further solenoid is energized above a given strength, said further solenoid being in a third circuit with said thermocouple.

6. A control arrangement comprising a conduit, means for moving air along said conduit, a burner including a shield positioned in said conduit, said shield reducing the air fiow in a first location downstream of and adjacent said shield but not reducing the air flow in a second location within said conduit elsewhere of said first location, said burner having an orifice arranged to exhaust fuel at said first location, an electric heater at said first location for igniting said fuel, a power supply in a first circuit with said electric heater, a thermocouple having a hot junction at said first location and a cold junction at said second location, a humidity responsive switch in said first circuit which switch is closed to complete said first circuit when the humidity rises above a predetermined value and is open to break said first circuit when the humidity falls below a predetermined value, a fuel valve controlling flow of fuel to said orifice, a solenoid in a second circuit with said power supply and controlling said fuel valve and arranged to open said valve when said solenoid is energized, said valve including means normally maintaining said valve in closed position except when said solenoid is energized, a relay including a further solenoid and a first set of contacts in said first circuit which are closed to complete said first circuit when said further solenoid is energized below a given strength, said relay including a second set of contacts in said second circuit which are closed to complete said second circuit when said further solenoid is energized above said given strength, said further solenoid being in a third circuit with said thermocouple.

7. A control arrangement comprising a shield, means operable to move a stream of air toward and past said shield, an electrical power source, an electric igniter within said shield, a thermocouple adjacent said igniter, said thermocouple having one junction within said shield and the other junction outside of said shield, electrically actuated means for feeding a combustible mixture to said shield, means for alternatively electrically connecting either said power source and igniter or said power source and feeding means, said connecting means being biased to maintain said power source and igniter electrically connected but operable by a potential of given strength to disconnect said power source and igniter and to connect said power source and feeding means, and a circuit connecting said thermocouple to said connecting means whereby production of an electric potential of given strength by said thermocouple operates said connecting means against said bias.

8. A sensing arrangement comprising means operable to move a stream of air, a shield positioned in the air stream and reducing the air flow in a first location downstream of and adjacent said shield but not reducing the air flow in a second location elsewhere of said first location, a thermocouple having a hot junction at said first location and a cold junction at said second location, means operable independently of said stream moving means to produce heat within the shield, said hot and cold junctions being spaced sufficiently close to one another and said thermocouple being of such thermal conductivity between said hot and cold junctions that said thermocouple produces a substantially greater voltage whenever the air moving means and said heat producing means are both operating than when one or both of said means is not operating.

9. A sensing arrangement comprising a thermocouple having a hot junction and a cold junction, first means operable to change the temperature of one of said junctions, second means operable independently of said first means for moving a stream of fluid over and past the other of said junctions, said thermocouple including material connecting said junctions which material is sufiiciently thermally conductive that the temperature of one junction is substantially the same as that of the other junction except when said second means is operating but whether or not said first means is operating whereby said thermocouple produces a substantial voltage whenever both of said means are operating but produces relatively little voltage whenever either or both of said means is not operating.

10. A control arrangement comprising a thermocouple having a hot junction and a cold junction, first means operable to produce heat at said hot junction, second means operable independently of said first means for moving a stream of air over and past the other of said junctions, said thermocouple including material connecting said junctions which material is sufiiciently thermally conductive that the temperature of one junction is substantially the same as that of the other junction except when said second means is operating but whether or not said first means is operating whereby said thermocouple produces a substantial voltage whenever both of said means are operating but produces relatively little voltage whenever either or both of said means is not operating.

References Cited in the file of this patent UNITED STATES PATENTS 1,773,612 Brady et al Aug. 19, 1930 2,474,547 Patch June 28, 1949 2,891,610 Wolff June 23, 1959 2,931,431 Iager et al. Apr. 5, 1960 3,027,932 Huber Apr. 3, 1962 

10. A CONTROL ARRANGEMENT COMPRISING A THERMOCOUPLE HAVING A HOT JUNCTION AND A COLD JUNCTION, FIRST MEANS OPERABLE TO PRODUCE HEAT AT SAID HOT JUNCTION, SECOND MEANS OPERABLE INDEPENDENTLY OF SAID FIRST MEANS FOR MOVING A STREAM OF AIR OVER AND PAST THE OTHER OF SAID JUNCTIONS, SAID THERMOCOUPLE INCLUDING MATERIAL CONNECTING SAID JUNCTIONS WHICH MATERIAL IS SUFFICIENTLY THERMALLY CONDUCTIVE THAT THE TEMPERATURE OF ONE JUNCTION IS SUBSTANTIALLY THE SAME AS THAT OF THE OTHER JUNCTION EXCEPT WHEN SAID SECOND MEANS IS OPERATING BUT WHETHER OR NOT SAID FIRST MEANS IS OPERATING WHEREBY SAID THERMOCOUPLE PRODUCES A SUBSTANTIAL VOLTAGE WHENEVER BOTH OF SAID MEANS ARE OPERATING BUT PRODUCES RELATIVELY LITTLE VOLTAGE WHENEVER EITHER OR BOTH OF SAID MEANS IS NOT OPERATING. 